Design of a Low-profile Ultra-wideband Antenna Array Based on Planar Dipole Elements

A low-profile ultra-wideband antenna array for the phased array applications has been proposed in this article. In order to meet both the low-profile and ultra-wideband requirements, the antenna array is composed of planar dipole elements fed by a microstrip-coupled structure. The feeding method is optimized by using a vertical transition. The thickness of the antenna array is approximately 20 mm, which is less than one-tenth of the wavelength at the lower frequency. Simulated results indicate that the operating frequency range with VSWR < 2.0 (in the normal direction) is from 1.3 GHz to 3.3 GHz (87.0% relative bandwidth). The operating frequency range has satisfied specific requirements of the specific project. It can be further expanded if required. The active VSWR versus the different scan angles are then calculated. The obtained results show that the active VSWR is less than 2.0 and 3.0 in the band 1.3 similar to 3.3 GHz while the range of scan angle is +/- 30 degrees and +/- 45 degrees, respectively. An 8x8 array is fabricated for the performance verification and the radiation patterns are measured in an anechoic chamber. Measured results confirm that this antenna array can be used properly in the phased array for compact applications.